(a) Field of the Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to a liquid crystal display which displays color images in a temporal division manner.
(b) Description of the Related Art
Generally, a liquid crystal display device includes an upper panel on which a common electrode and color filters are formed, a lower panel on which thin film transistors and pixel electrodes are formed, and a liquid crystal layer disposed between the upper and lower panels. When applying a potential difference to the pixel electrodes and the common electrode, an electric field is generated in the liquid crystal layer, and the orientation of liquid crystal is determined on the basis of the electric field. Since the transmittance of incident light is determined on the basis of the aligned direction of liquid crystal molecules, it is possible to display a desired image by adjusting the potential difference between the two electrodes.
In order to realize color representation in such a liquid crystal display, each pixel displays any one of the primary colors such as red, green and blue, for example. Alternatively, all of the pixels each display the primary colors such as red, green and blue, for example, as time passes. The former refers to a spatial division method and the latter refers to a temporal division method.
According to the spatial division method, red, green and blue color filters are disposed in regions corresponding to the pixel electrodes to display color images. In this case, the color images can be displayed by passing light emitted from a white light source such as a light emitting diode (“LED”) or a cold cathode fluorescent lamp (“CCFL”) through the liquid crystal layer and the color filters.
According to the temporal division method, the liquid crystal display displays color images by providing an additional light source which emits color light components. In this temporal division method, all pixels are scanned corresponding to the operation of a gate driver and a data driver, and then a red light source is turned on. Thereafter, all pixels are scanned again, and a green light source is turned on. Finally, all pixels are scanned again, and a blue light source is turned on. Therefore, three frames (hereinafter, referred to sub-frames) are performed during a time (about 16.6 ms) corresponding to one frame of the spatial division method. Therefore, the time for each of the sub-frames is reduced to about 5.5 ms or less, which is one third of the one frame time (e.g., 16.5 ms).
Thus, since data is scanned and the light sources are turned on for a short time of about 5.5 ms, the scanning and turning-on should be performed three-times faster speed than in the case of using color filters. Therefore, there is a problem in that the charging time of the liquid crystal capacitor is decreased, and the problem becomes more serious in the case of a large liquid crystal display device. Further, there is another problem in that desired color cannot be displayed due to a reduced turned-on time of the light source.
Therefore, there is a desire to improve the image quality of the display device by increasing the charge time of the pixels, and to secure the wide visibility of the liquid crystal display device.